1. Field of the Invention
The present invention relates to the new type Electro-Optical (E-O) crystal elements, its applications and the processes for the preparation thereof. More specifically, the present invention relates to an E-O crystal element showing super-high effective (transverse and longitudinal) linear E-O coefficient and very low half-wave voltage Vπ useful in a wide number of modulation, communication, laser, and electro-optical industrial uses.
2. Description of the Related Art
Recently PMN-PT based ferroelectric relaxor crystals have been well developed because of its super-high piezoelectric properties such as electrical strains an order higher than conventional piezoelectric materials and the electro-mechanical coupling factor over 90%. These crystals have been used for piezoelectric applications, especially for acoustic transduction devices, such as ultrasound imaging and sonar transducers. The very anisotropic piezoelectric characteristics of <011> poled PMN-PT and/or PZN-PT based crystals have been well documented. These can be noted in Applicant's prior publications, the entire contents of which are incorporated herein fully by reference:                P. Han, W. L. Yan, J. Tian, X. L. Huang, and H. X. Pan. “Cut directions for the optimization of piezoelectric coefficients of lead magnesium niobate—lead titanate ferroelectric crystals”. Discovery of d36 shear mode, Appl. Phys, Letter. 86, No. 1, 2466, (2005); and        P. Han, J. Tian, and W. Yan, “Bridgman growth and properties of PMN-PT single crystals,” in Advanced dielectric, piezoelectric and ferroelectric materials: Synthesis, characterization and applications, Z. G. Ye, Ed., 1st Ed: Woodhead Publishing Ltd., 2008, p. 600-632. (The summary of large-sized PMN-PT crystals growth by modified Bridgman method and characterizations).        
The linear E-O effects of <001> poled and <111> poled PMN-PT and PZN-PT ferroelectric crystals above have been reported, but the results were not encouraged or promoted as inoperative for commercial uses. These results were noted in the publications below, the entire contents of which are also incorporated herein fully by reference.                Yu Lu, Z. Y. Cheng, S. E. Park, S, F Liu and Q. M. “Zhang “linear Electro-Optic effect of 0.88Pb(Zn⅓Nb⅔)O3 single crystal”, Jpn. J Appl. Phys Vol. 39 No. 1, January, 2000.        X. M. Wan, D. Y. Wang, X. Y. Zhao, Haosu Luo, H. L. W. Chan and C. L. Choy. “Electro-Optic characterization of tetragonal (1−x)Ob(Mg⅓Nb⅔)O3 single crystals by a method Senarmont Setup” Slid state communications Vol. 134 547-551 (2005).        L. S. Kamzina, Ruan Wei, G. Li, J. Zeng and A. Ding. “Electro-Optical properties of PMN-PT compounds: single crystals and transparent ferroelectric ceramics”. Physics of solid state, Vol. 52. No. 10 2142-2146 (2010). (Original Russian text).        Enwei Sun, Zhu Wang, Rui Zhang and Wenwu Cao. “Reduction of electro-optic half-wave voltage of 0.93Pb(Zn⅓Nb⅔)3-0.07PbTiO3 single crystal through large piezoelectric strain”. Optical Materials Vol. 33.m 549-552 (2011).        
The major reason is the light scattering from multi-domain walls and the instability of <111> poled single domain status and that all the reported works were limited in optical uniaxial crystals of the PMN-PT or PZN-PT based solid solutions.